Why a hot air balloon rises into the air when the gas is heated?

A hot air balloon rises because heating the air inside the balloon decreases its density compared to the cooler air outside. As the air inside the balloon warms up, it expands and becomes lighter than the surrounding cooler air. This difference in density creates buoyancy, allowing the balloon to ascend. Essentially, the hot air becomes a source of lift, enabling the balloon to float upwards.